How to use the dog age calculator
- Enter your dog's age. Type years and months, or switch to Date of birth and pick the day your dog was born. For a puppy you can type the whole age in months, such as 0 years and 18 months.
- Choose the size, or type your dog's adult weight in pounds or kilograms and the size is picked for you.
The big number is your dog's age in human years from the size chart. Below it are the newer DNA formula's figure, the life stage, the usual senior age for that size, the age in months, and what the old "times 7" rule would say.
Between two whole years the calculator reads along a straight line between the chart's rows, so 7 years and 6 months for a large dog is halfway from 50 to 55, about 53.
Dog age chart: dog years to human years by size
The American Kennel Club (AKC) publishes this chart. The weights are the chart's own, in pounds; the kilograms are our conversion.
| Dog's age | Small, 20 lb or less (9.1 kg) | Medium, 21 to 50 lb (9.5 to 22.7 kg) | Large, 51 to 100 lb (23.1 to 45.4 kg) | Giant, over 100 lb (45.4 kg) |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 12 |
| 2 | 24 | 24 | 24 | 22 |
| 3 | 28 | 28 | 28 | 31 |
| 4 | 32 | 32 | 32 | 38 |
| 5 | 36 | 36 | 36 | 45 |
| 6 | 40 | 42 | 45 | 49 |
| 7 | 44 | 47 | 50 | 56 |
| 8 | 48 | 51 | 55 | 64 |
| 9 | 52 | 56 | 61 | 71 |
| 10 | 56 | 60 | 66 | 79 |
| 11 | 60 | 65 | 72 | 86 |
| 12 | 64 | 69 | 77 | 93 |
| 13 | 68 | 74 | 82 | 100 |
| 14 | 72 | 78 | 88 | 107 |
| 15 | 76 | 83 | 93 | 114 |
| 16 | 80 | 87 | 99 | 121 |
The American Veterinary Medical Association (AVMA) has its own chart, for one size only, a medium dog. Its footnote reads:
"Based on a medium-sized dog weighing 21-50lbs."AVMA, Pets age faster than people
All 16 of its figures are the same as the Medium column above. The pattern is the one UC Davis gives as the AVMA and AKC guideline: 15 human years for a medium dog's first year, 9 for the second, and then about 5 a year (4 to 6 on the chart). Small dogs age more slowly after that and giant dogs faster, which is why size changes the answer.
Dog age calculator by breed, weight or size
The chart works by size, not breed, so a breed is placed by its adult weight. A dog that weighs 25 lb as an adult uses the Medium column, and one of 70 lb the Large column. For a mixed breed, or a dog that is not fully grown, use the weight the dog is expected to reach as an adult. Typing the weight picks the column: up to 20 lb is small, over 20 up to 50 lb medium, over 50 up to 100 lb large, and over 100 lb giant.
The AVMA says when dogs of each size are usually considered senior, using slightly different weight bands from the chart:
| Size (AVMA's weights) | Senior from about |
|---|---|
| Small or toy, less than 20 lb | 8 to 11 years |
| Medium, 20 to 50 lb | 8 to 10 years |
| Large, 50 to 90 lb | 8 to 9 years |
| Giant, more than 90 lb | 6 to 7 years |
The calculator matches these by size name, so a 95 lb dog is Large on the chart but in the AVMA's giant band.
Puppy age in human years
The size chart starts at 1 year, so for a puppy the calculator shows the milestone comparison that UC Davis School of Veterinary Medicine gives from the UC San Diego study of Labrador retrievers:
| Dog's age | Like a person's |
|---|---|
| First 8 weeks | first 9 months |
| 2 to 6 months | 1 to 12 years |
| 6 months to 2 years | 12 to 25 years |
The DNA formula below puts a 4-month-old puppy at about 13. By the chart, a 1-year-old small, medium or large dog is already 15.
The UC San Diego DNA formula
In 2020 researchers at UC San Diego compared age-related changes in the DNA (methylation) of Labrador retrievers with those of people. The paper in Cell Systems combines two fitted curves into one:
"human_age = 16 ln(dog_age) + 31"Wang et al., Cell Systems, 2020
Here ln is the natural logarithm and the dog's age is in years.
| Dog's age | 16 ln(age) + 31 |
|---|---|
| 1 year | 31 |
| 2 years | 42 |
| 4 years | 53 |
| 7 years | 62 |
| 10 years | 68 |
| 16 years | 75 |
Read it with care. The dogs were Labradors aged 0.1 to 16 years, and the paper says other breeds "could yield different age-translation functions." The curve rises very steeply in the first months and gives zero or less below about 7.5 weeks, so the calculator shows it only from 8 weeks old, and flags it past 16 years.
Why the 7 years rule is a myth
The AVMA is plain about it: dogs "do not age at a rate of 7 human years per dog year." UC Davis notes that the rule probably came from average lifespans of about 10 years for dogs and 70 for people, and that dogs age much faster than people in their first years. UC San Diego's news story makes the same point: a nine-month-old dog can have puppies.
Dog life stages
The 2019 AAHA Canine Life Stage Guidelines use five stages:
- Puppy: birth until rapid growth stops, at about 6 to 9 months depending on breed and size.
- Young adult: until the dog is fully mature, in most dogs by 3 to 4 years.
- Mature adult: until the last 25% of the expected lifespan.
- Senior: the last 25% of the expected lifespan.
- End of life: a stage set by health, not age.
The calculator uses those ages and the AVMA senior ages above. Where the guides give a range it says so, for example "Mature adult or senior" for a 9-year-old small dog.
In Excel or Google Sheets
With the dog's age in years in A2, the DNA formula is =16*LN(A2)+31. LN is the natural logarithm in both Excel and Google Sheets. With the date of birth in B2, =DATEDIF(B2,TODAY(),"y") gives the age in whole years. For a dog born on February 29, this calculator counts February 28 as the birthday in common years, as many places do; spreadsheets and some other tools may count March 1 instead.
Questions and answers
How old is my dog in human years?
It depends on age and size. On the AKC chart a 10-year-old dog is 56 if small, 60 if medium, 66 if large and 79 if giant. Enter your dog's age and size above for yours.
Is one dog year really seven human years?
No. The AVMA says dogs do not age at a rate of 7 human years per dog year. Dogs grow up much faster at first: a 1-year-old dog is about 15 in human years, and a 2-year-old about 24.
How do I work out dog years by weight?
Use your dog's adult weight to pick the size: 20 lb or less is small, 21 to 50 lb medium, 51 to 100 lb large and over 100 lb giant. Then read the row for your dog's age. Typing the weight above does this for you.
How old is a 6-month-old puppy in human years?
The UC San Diego study, as summarized by UC Davis, puts 2 to 6 months of a dog's life alongside 1 to 12 years of a person's, and 6 months to 2 years alongside 12 to 25. The DNA formula gives about 20 for 6 months.
At what age is a dog a senior?
The AVMA gives about 8 to 11 years for small dogs, 8 to 10 for medium, 8 to 9 for large and 6 to 7 for giant breeds, the point where a dog reaches the last 25% of its expected lifespan.
Which is more accurate, the chart or the DNA formula?
Neither is exact for one dog. The chart allows for size; the DNA formula comes from Labradors only. Use them as a rough guide and ask your vet about your own dog's health.
Sources
Checked on 8 October 2026. If a rule has changed, please tell us.
- American Kennel Club: How to calculate dog years to human years (size chart)
- AVMA: Pets age faster than people (medium-sized dog chart, PDF)
- AVMA: Caring for senior cats and dogs (senior ages by size)
- AAHA: 2019 Canine Life Stage Guidelines (PDF)
- UC Davis School of Veterinary Medicine: Calculating Your Dog's Age
- Wang et al., Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome, Cell Systems 11(2), 2020
- UC San Diego Today: How old is your dog in human years? (2 July 2020)
- Microsoft Support: LN function
- Google Docs Editors Help: LN
- Microsoft Support: DATEDIF function